Age and fertility

Age affects the fertility of both men and women, and it is the single biggest factor affecting a woman’s chance to conceive and have a healthy baby.

Women’s age and fertility#

A woman is born with all the eggs she will ever have. Her eggs age with her, declining in both quality and quantity. Age is the single most important factor affecting a woman’s fertility. Being in good health improves the chance of getting pregnant, but it does not override the effects of age.

A woman in her early to mid-20s has about a 25 to 30 per cent chance of getting pregnant in each monthly cycle. Fertility generally starts to slowly decline when a woman is in her early 30s, and after the age of 35 the decline speeds up. By age 40, the chance of getting pregnant in any monthly cycle is around 5 per cent.

Women’s age and IVF#

A woman’s age also affects the chance of success with IVF. It is a common misconception that IVF treatment can override the effects of age. The chance of a live birth from one complete IVF cycle, which includes all fresh and frozen-thawed embryo transfers following one ovarian stimulation, is about:

• 43 per cent for women aged 30 to 34 years
• 31 per cent for women aged 35 to 39 years
• 11 per cent for women aged 40 to 44 years

For older women, the chance of having a baby increases if they use donated eggs.

Women’s age and pregnancy complications#

The risk of pregnancy complications also increases with age. The risk of miscarriage and of chromosomal abnormalities in the fetus rises from age 35. Other complications that become more likely include gestational diabetes, placenta praevia, caesarean birth and stillbirth.

Some conditions that may affect a woman’s fertility, such as endometriosis and polycystic ovary syndrome (PCOS), can also play a role.

Men’s age and fertility#

While the effects of female age on fertility have been understood for a long time, more recent studies have found that the age of the male partner also affects the chance of pregnancy and the health of a pregnancy.

Increasing male age reduces the overall chance of pregnancy, increases the time it takes to conceive, and raises the risk of miscarriage and fetal death, although this remains rare. Children of fathers aged 40 or over are around five times more likely to develop autism spectrum disorder and other mental health conditions later in life than children of fathers aged 30 or under. They also have a slightly increased risk of developing schizophrenia.

Key points#

• Age is the single most important factor affecting a woman’s fertility and her chance of having a healthy baby.
• Fertility declines slowly from a woman’s early 30s and more quickly after 35.
• A woman’s age also affects the chance of success with IVF, and good health does not override the effects of age.
• The age of the male partner also affects the chance of pregnancy and the health of a pregnancy.

Where to get help#